Microstrip patch antenna and method

Abstract

Method and apparatus are provided for a microstrip feeder structure for supplying properly phased signals to each radiator element in a microstrip antenna array that may be utilized for radiating circularly polarized electromagnetic waves. In one disclosed embodiment, the microstrip feeder structure includes a plurality of microstrip sections many or all of which preferably have an electrical length substantially equal to one-quarter wavelength at the antenna operating frequency. The feeder structure provides a low loss feed structure that may be duplicated multiple times through a set of rotations and translations to provide a radiating array of the desired size.

What is claimed is:  
     
       1. A method for a microstrip feeder structure for a microstrip antenna array, said microstrip antenna array having a plurality of radiating elements and an antenna operating frequency, each of said radiating elements having a radiation resistance at resonance, said method comprising: 
       providing first and second microstrip feed lines for connecting to each of said radiating elements, said first and second feed lines each having an electrical length of approximately one-quarter wavelength at said antenna operating frequency, said first and second feed lines having identical characteristic impedances equal to a first characteristic impedance;  
       providing a third microstrip section in series with said first microstrip feed line;  
       selecting a length of said third microstrip section to provide a ninety-degree phase shift;  
       selecting said third microstrip section to provide a third characteristic impedance equal to the impedance looking into said first feed line toward a respective one of said plurality of radiating elements; and  
       connecting an end of said third microstrip section and an end of said second microstip section together to form a first joint.  
     
     
       2. The method of claim  1 , further comprising: 
       providing a fourth microstrip section connected to said first joint;  
       providing a fifth microstrip section connected in series to said fourth microstrip section;  
       adjusting an impedance looking into said fifth microstrip section toward said respective one of said radiating elements to provide an adjusted impedance by selecting a fourth characteristic impedance for said fourth microstrip section and a fifth characteristic impedance for said fifth microstrip section.  
     
     
       3. The method of claim  2 , further comprising: 
       providing that said first, second, third, fourth, and fifth microstrip sections form a Tier 1-Circuit A; and  
       copying and rotating said Tier 1-Circuit A to provide a Tier 1-Circuit B.  
     
     
       4. The method of claim  3 , further comprising: 
       selecting said rotating to be clockwise or counterclockwise for providing either left-handed or right-handed polarization, respectively, for said microstrip antenna array.  
     
     
       5. The method of claim  4 , further comprising: 
       providing a Circuit A sixth microstrip section connected in series to said fifth section of said Tier 1-Circuit A,  
       providing a Circuit B sixth microstrip section connected in series to said fifth section of said Tier 1-Circuit B,  
       providing said Circuit A and said Circuit B sixth microstrip sections with a characteristic impedance equal to an impedance looking into said fifth microstrip section, and  
       providing that said Circuit A sixth microstrip section and said circuit B sixth microstrip section differ in an electrical length related to an amount corresponding to angle of rotation of said Tier 1-Circuit A with respect to said Tier 1-Circuit B.  
     
     
       6. The method of claim  5 , further comprising: 
       providing a Circuit A seventh microstrip section in series with said Circuit A sixth microstrip section,  
       providing a Circuit B seventh microstrip section in series with said Circuit B seventh microstrip section, and  
       joining respective ends of said Circuit A seventh microstrip section and said Circuit B seventh microstrip sections to form a second joint.  
     
     
       7. The method of claim  6 , further comprising: 
       providing a two-element microstrip antenna array by connecting an eighth microstrip section to said second joint.  
     
     
       8. The method of claim  6 , further comprising: 
       providing that said Tier 1-Circuit A and said Tier 1-Circuit B collectively form a Tier 2-Circuit A,  
       providing a four-element microstrip antenna array by copying and rotating said Tier 2-Circuit A to provide a Tier 2-Circuit B, and  
       connecting a Circuit A eighth microstrip section and a Circuit B eighth microstrip section, respectively, to said second joint of each of said Tier 2-Circuit A and said Tier 2-Circuit B.  
     
     
       9. A microstrip feeder structure for a microstrip antenna array, said microstrip antenna array having a plurality of radiating elements and an antenna operating frequency, each of said radiating elements having a radiation resistance at resonance, said microstrip feeder structure comprising: 
       first and second microstrip feed lines for connecting with each of said radiating elements, said first and second microstrip lines each having a substantially identical first characteristic impedance and a substantially identical first electrical length equal to one-quarter wavelength at said antenna operating frequency; and  
       a third microstrip section in series with said second microstrip feed line having an electrical length of one-quarter of a wavelength, said third microstrip section having a third characteristic impedance related to a square of said first characteristic impedance divided by said radiation resistance, said third microstrip section providing a ninety-degree phase shift of a feed signal, said third microstrip section being electrically connected to said first microstrip feed line at a first joint.  
     
     
       10. The microstrip feeder structure of claim  9 , further comprising: 
       a fourth microstrip section being electrically connected to said first joint, said fourth microstrip section having a fourth characteristic impedance,  
       a fifth microstrip section having first and second opposing ends with said first end making a series connection with said fourth microstrip section, said fifth microstrip section having a fifth characteristic impedance, an adjusted line impedance looking into said second end of said fifth microstrip section toward said first end being related to said third characteristic impedance times a ratio of said fourth and fifth characteristic impedances.  
     
     
       11. The microstrip feeder structure of claim  10 , further comprising: 
       said adjusted line impedance looking into said second end of said fifth microstrip section toward said first end being equal to said third characteristic impedance divided by two with the result being multiplied times a squared ratio of said fifth characteristic impedance divided by said fourth characteristic impedance.  
     
     
       12. The microstrip feeder structure of claim  11 , further comprising: 
       said first, second, third, fourth, and fifth microstrip sections forming a Tier 1 circuit for feeding each of said radiating elements.  
     
     
       13. The microstrip feeder structure of claim  12 , further comprising: 
       two of said Tier 1 circuits which are rotated with respect to each other to form a Tier 1 -Circuit A and a Tier 1 -Circuit B, respectively.  
     
     
       14. The microstrip feeder structure of claim  13 , further comprising: 
       a Circuit A sixth microstrip section connected to said Tier 1 -Circuit A, and  
       a Circuit B sixth microstrip section connected to said Tier 1 -Circuit B.  
     
     
       15. The microstrip feeder structure of claim  13 , further comprising: 
       said Circuit A sixth microstrip section and said Circuit B sixth microstrip section having a difference in respective electrical lengths related to an angle of rotation between said Tier 1 -Circuit A and said Tier 1 -Circuit B.  
     
     
       16. The microstrip feeder structure of claim  15 , further comprising 
       said Circuit A sixth microstrip section and said Circuit B sixth microstrip section each having a characteristic impedance equal to an impedance seen looking into a respective said fifth microstrip section.  
     
     
       17. The microstrip feeder structure of claim  16 , further comprising 
       a Circuit A seventh microstrip section in series with said Circuit A sixth microstrip section, and  
       a Circuit B seventh microstrip section in series with said Circuit B sixth microstrip section, said Circuit A seventh microstrip section and said Circuit B seventh microstrip section being connected to form a second joint.  
     
     
       18. The microstrip feeder structure of claim  17 , further comprising 
       said Tier 1 -Circuit A including said Circuit A sixth microstrip section and said Circuit A seventh microstrip section combining with said Tier 1 -Circuit B including said Circuit B sixth microstrip section and said Circuit B seventh microstrip section to form a Tier 2 -Circuit A, and  
       a copy of said Tier 2 -Circuit A rotated with respect to said Tier 2 -Circuit A to form a Tier 2 -Circuit B.  
     
     
       19. A microstrip feeder structure for a microstrip antenna array, said microstrip antenna array including a plurality of radiating elements, each of said radiating elements having a radiation resistance at resonance, said microstrip feeder structure comprising: 
       a plurality of first microstrip sections having an electrical length of one-quarter wavelength, each of said plurality of first microstrip sections terminating at one end with a respective one of said plurality of radiating elements;  
       a plurality of second microstrip sections having an electrical length of one-quarter wavelength, each of said plurality of second microstrip sections terminating at one end with said respective one of said plurality of radiating elements;  
       a plurality of third microstrip sections having an electrical length of one-quarter wavelength, each of said plurality of third microstrip sections connecting at one end to respective of said plurality of second microstrip sections, each of said plurality of third microstrip sections connecting at an opposite end to respective of said plurality of first microstrip sections to form a plurality of first joints;  
       a plurality of fourth microstrip sections, each of said plurality of fourth microstrip sections connecting at one end to a respective one of said plurality of first joints;  
       a plurality of fifth microstrip sections, each of said plurality of fifth microstrip sections connecting at one end to a respective of said plurality of fourth microstrip sections, each of said plurality of first, second, third, fourth, and fifth microstrip sections forming a plurality of Tier 1 circuits, each said plurality of Tier 1 circuits being rotated with respect to each other, one-half of said Tier 1 circuits being designated as a Tier 1 -Circuit A and one-half of said Tier 1 circuits being designated a Tier 1 -Circuit B.  
     
     
       20. The microstrip feeder structure of claim  19 , further comprising: 
       a Circuit A sixth microstrip section connected to each said Tier 1 -Circuit A, and  
       a Circuit B sixth microstrip section connected to each said Tier 1 -Circuit B, said Circuit A sixth microstrip section and said Circuit B sixth microstrip section having an electrical length differing with respect to each other by an angle of rotation between each said Tier 1 -Circuit A and said Tier 1 -Circuit B.  
     
     
       21. The microstrip feeder structure of claim  20 , further comprising: 
       a Circuit A seventh microstrip section connecting to each Circuit A sixth microstrip section, and  
       a Circuit B seventh microstrip section connecting to each Circuit B sixth microstrip section, said Circuit A seventh microstrip section connecting to said Circuit B seventh microstrip section.  
     
     
       22. The microstrip feeder structure of claim  21 , further comprising: 
       each said Tier 1-Circuit A and said Circuit A sixth microstrip section and said Circuit A seventh microstrip section and said Tier 1-Circuit B and said Circuit B sixth microstrip section and said Circuit B seventh microstrip section forming a Tier 2-Circuit A, and  
       a Tier 2-Circuit B identical to said Tier 2-Circuit A being rotated with respect to said Tier 2-Circuit A.  
     
     
       23. The microstrip feeder structure of claim  22 , further comprising: 
       a circuit A eighth microstrip section connecting to said Tier 2-Circuit A, and  
       a circuit B eighth microstrip section connecting to said Tier 2-Circuit B.  
     
     
       24. The microstrip feeder structure of claim  23 , further comprising: 
       said circuit A eighth microstrip section varying in electrical length with respect to said circuit B eighth microstrip section by an amount related to an angle of rotation of said Tier 2-Circuit A with respect to said Tier 2-Circuit B.  
     
     
       25. The microstrip feeder structure of claim  19 , further comprising: 
       said first and second microstrip sections each having an identical smoothly curved shape and having an identical characteristic impedance.  
     
     
       26. The microstrip feeder structure of claim  19 , further comprising: 
       said third microstrip sections having a smoothly curved configuration.  
     
     
       27. The microstrip feeder structure of claim  19 , further comprising: 
       said fourth microstrip sections being substantially straight.  
     
     
       28. The microstrip feeder structure of claim  19 , further comprising: 
       said fifth microstrip sections including a substantially U-shaped portion.  
     
     
       29. A microstrip feeder structure for a microstrip antenna array, said microstrip antenna array including a plurality of radiating elements, each of said radiating elements having a radiation resistance at resonance, said microstrip feeder structure comprising: 
       a Tier 1-Circuit A comprising a Circuit A radiating element and a Circuit A feed structure;  
       a Tier 1- Circuit B comprising a Circuit B radiating element and a Circuit B feed structure;  
       said Tier 1-Circuit A and said Tier 1-Circuit B forming a Tier 2-Circuit A;  
       a Tier 2-Circuit B identical to said Tier 1-Circuit A and rotated by an angle of rotation with respect to said Tier 1-Circuit A;  
       a Circuit A microstrip section connected to a Tier 2-Circuit A connection point of said Tier 2-Circuit A;  
       a Circuit B microstrip section connected to a Tier 2-Circuit B connection point of said Tier 2-Circuit B, said Circuit A microstrip section and said Circuit B microstrip section having an identical characteristic impedance, said characteristic impedance being equal to an impedance looking into either of said respective Tier 2-Circuit A connection point or said Tier 2-Circuit B connection point, said Circuit A microstrip section and said Circuit B microstrip section having an electrical length that differs with respect to each other by an electrical length related to said angle of rotation, said Circuit A microstrip section and said Circuit B microstrip section being connected to each other.